Numerous gas generators currently commercially available make use of energetic pyrotechnical charges constituted by propellants. These products, whether extruded or compressed, are adapted with respect to their form and their composition to satisfy the needs of gas generation.
However, these products have considerable added value, therefore high cost. Also, they have a yield which is limited, first by the specifications relative to the levels of toxicity and second by the possibilities of formulating the low-cost main molecules, available commercially.
The document WO-A-01/89885 describes a generator structure which makes use of a charge of energetic matter having a high gaseous yield and at a low cost placed in a first chamber, which is decomposed by a gas jet originating from a combustion chamber in which a propellant burns.
The charges described are respectively strongly oxidising ammonium nitrate, which is associated with a strongly reductive propellant (of “LOVA” type (for “Low Vulnerability Ammunition”), or double base, or any other propellant adapted to need).
The gas jet originating from the combustion chamber passes through a diffusion chamber and enters the chamber containing the ammonium nitrate.
The diffusion chamber is thus the seat of an oxidoreducing reaction between the gases generated by the propellant and those originating from combustion of the ammonium nitrate.
This chemical interaction accordingly takes place in a chamber which is not confined or only slightly confined.
Another existing structure makes use of a propellant whereof the oxygen balance is equilibrated, which disintegrates an oxidoreducing mixture whereof the oxygen balance is likewise equilibrated.
In these two structures, the energetic charge is in the form of powder whereof the granulometry is much less than a millimeter (typically from 10 to 200 micrometers). This involves a very brief decomposition time, incompatible with the operating time expected by the system.
US-A-2006/0005734 describes a gas generator whereof the central diffusion chamber is enclosed by two combustion chambers, in turn arranged in the continuity of an initiator. Each chamber is to some extent “double”. Therefore, on the left part of the generator, the initiator communicates with a chamber which contains a relay pyrotechnical charge, in turn relating to a chamber containing the gas-generating charge.
However, the relay charge is there only for initiating, that is, triggering combustion of the pyrotechnical charge.
In the event where the aim is to generate little gas, use is made of a single pyrotechnical charge.
Document EP-A-1323696 describes a gas-generating device which comprises a first charge, the initiation of which causes that of a second oxidoreducing charge with an equilibrated oxygen balance. It is the flow of combustion products which causes initiation of the second charge.
Finally, documents EP-A-1364845 and US-A-2005/230949 describe generators whereof the functioning is similar to that described in the above paragraph.